The aim of this product is to provide an efficient rendering solution to for volumetric cloud scenes. The HDRI's provided with the product feature pre-rendered and Bryce captured volumetric clouds combined with a real sun and moon. The example scenes provided demonstrate how the HDRI supplied can be used in conjunction with the advanced and powerful IBL features found in Bryce 7 Pro to produce a range of pleasing skies in scenes that are designed to render quickly or at least efficiently depending on the power of your computer processor.
The authors have also provided accompanying videos, both technical and practical and a PDF to assist in the use of this product. Having said that, I think it would be fair to suggest Bryce IBL novices learn a little bit about HDRI before considering this product.
Horo has thoughtfully provided the following videos on this very topic.
Bryce 7 Using Image Based Lighting IBL part 1 of 3
Bryce 7 Using Image Based Lighting IBL part 2 of 3
Bryce 7 Using Image Based Lighting IBL part 3 of 3